This invention relates generally to the comminution and dehydration of municipal sludge utilizing a cyclonic comminuter and, more particularly, to the process of treating municipal sewage sludge and related materials, as a pretreatment conditioner for further appropriate treatment of the output material.
An environmentally acceptable treatment of municipal sewage sludge has become an important issue. The disposal of municipal sludge with a high percentage of moisture can be accomplished by composting, but the transport of the material to the composting site involves the transportation of 30%-40% moisture, which increases the overall cost of disposing of the municipal sludge material. Accordingly, a process, method and apparatus for pre-treating municipal sludge material to create an output that is acceptable for further processing treatment in a cost effective way would be highly desirable. Such a process, however, must also be effective in the removal of pathogens from the waste product being treated.
It is an object of this invention to provide a method of processing municipal waste to effect a comminution and a dehydration thereof by feeding said sludge material into a cyclonic comminuter.
It is another object of this invention to provide a method of processing municipal sludge waste including the steps of feeding the sludge into the air flow of a cyclonic dehumidifying comminuter to comminute the sludge and to effect dehydration thereof, the comminuted and dehydrated sludge being discharged through a material discharge opening at a bottom portion of the cyclonic comminuter while moisture laden air flow is discharged through an air discharge opening;
sterilizing the discharged air flow after being exhausted from said comminuter to remove pathogens therefrom before being released to the atmosphere; and
passing the comminuted and dehydrated sludge material through a sterilization chamber after being discharged from the cyclonic comminuter to destroy pathogens therein.
It is a feature of this invention that the flow rate of the municipal sludge through the cyclonic comminuter can be controlled to establish a desired moisture content of the comminuted and dehydrated sludge being discharged from the cyclonic comminuter.
It is an advantage of this invention that the comminuted and dehydrated municipal sludge being discharged from the cyclonic comminuter can be further processed by pelletizing or by further drying into a powder for shipment thereof to a remote location, after sterilization.
It is another feature of this invention that an auger can be used for metering the flow of municipal sludge into the infeed of the cyclonic comminuter.
It is another advantage of this invention that the auger used for metering the flow of the sludge waste into the infeed of the cyclonic comminuter will mix different supplies of waste materials containing different moisture levels for feeding into the cyclonic comminuter.
It is still another feature of this invention that the comminuted and dehydrated sludge and the moisture laden air flow discharged from the cyclonic comminuter are sterilized to remove pathogens therefrom.
These and other objects, features, and advantages are accomplished according to the instant invention by providing a process for the comminution and dehydration of municipal sludge waste by feeding the municipal sludge waste into a cyclonic, dehydrating comminuter to facilitate the further processing of the comminuted and dehydrated sludge material discharged from the comminuter. Both the comminuted and dehydrated sludge material and the air flow discharged from the cyclonic comminuter are sterilized to remove pathogens therefrom. The rate at which the municipal sludge material is fed into the cyclonic comminuter is directly related to the moisture content of the comminuted and dehydrated material discharged from the material discharge opening of the comminuter. Preferably, the moisture content of the discharged material is in the range of 25% to 35% to facilitate the sterilization of the discharged material. An alternative process can be used, however, to dry the discharged comminuted and dehydrated municipal sludge waste material to about 10%, such as by passing the material discharged from the first cyclonic dehydrating comminuter into a second cyclonic dehydrating comminuter until the finally discharged material has a powdery consistency.